1. Field of the Invention
The present invention relates to a CCD-type solid-state imaging device, a driving method applied to the CCD-type solid-state imaging device, and an imaging system including the CCD-type solid-state imaging device.
2. Description of the Related Art
In related art, a CCD (Charge Coupled Device)-type solid-state imaging device is known as a solid-state imaging device. The CCD-type solid-state imaging device has a configuration to obtain image signals by sequentially transferring charge accumulated in light receiving devices forming pixels using a CCD as a charge coupled device and outputting it.
FIG. 7 shows an example of a CCD-type solid-state imaging device in related art.
The explanation of the configuration of FIG. 7 is as follows. A CCD-type solid-state imaging device 10 includes an imaging region 20, and photodiodes 21 as light receiving devices forming pixels arranged in predetermined numbers in the horizontal direction and the vertical direction within the imaging region. In each photodiode 21, signal charge is accumulated by receiving light.
In the example of FIG. 7, photodiodes 2111, 2112, . . . , 211n are arranged on a vertical line at the left end, and photodiodes 2121, 2122, . . . , 212n are arranged on a vertical line on the immediately right. In this way, photodiodes 21m1, 21m2, . . . , 21mn are arranged on a vertical line at the right end. The n in this specification is the number of pixels in the vertical direction and m is the number of pixels in the horizontal direction. Accordingly, the photodiodes 21 are arranged in a matrix of n in the vertical direction and m in the horizontal direction.
On the sides of the photodiodes 2111 to 211n, 2121 to 212n, . . . , 21m1 to 21mn, vertical transfer channels 221, 222, . . . , 22n are arranged. The vertical transfer channels 221 to 22n include CCDs as charge coupled devices and transfer charge. As shown in FIG. 7, in the respective vertical transfer channels 221 to 22n, transfer electrodes 2311 to 23mn and readout-transfer electrodes 2411 to 24mn are alternately arranged. The readout-transfer electrodes 2411 to 24mn read out signal charge accumulated in the adjacent photodiodes 2111 to 21mn, and transfer the read out signal charge (or transferred signal charge) to the next transfer electrodes (the lower electrodes in the drawing). The transfer electrodes 2311 to 23mn transfer the charge transferred from the upper electrodes 24 to the lower electrodes 24.
The readout operation and the transfer operation in these readout-transfer electrodes 2411 to 24mn and the transfer operation in the transfer electrodes 2311 to 23mn are performed in synchronization with a vertical transfer clock externally supplied via an input terminal 11a or the like.
To the lower ends of the respective vertical transfer channels 221 to 22n, a horizontal transfer channel 25 is connected, and the charge transferred in the respective vertical transfer channels 221 to 22n is supplied to different electrode positions of the horizontal transfer channel 25 with respect to each vertical line. The charge transferred to the horizontal transfer channel 25 is supplied to an output circuit 13 connected to the end of the horizontal transfer channel 25 in synchronization with a horizontal transfer clock, and imaging signals are externally output from an output terminal 14 connected to the output circuit 13.
Thus far, a general configuration as the CCD-type solid-state imaging device has been explained.
Further, the CCD-type solid-state imaging device 10 in the example of FIG. 7 supplies the clocks for controlling the readout operation and the transfer operation in the readout-transfer electrodes 2411 to 21mn within the vertical transfer channels 221 to 22n to the respective electrodes 2411 to 24mn from the input terminal 11a via a resistor 12. The resistor 12 may have a resistance value of about several tens of ohms to several hundreds of ohms, for example. To supply the clock via the resistor 12 is for the purpose of making the pulse waveform of the transfer clock proper. The specific examples of the pulse waveform will be described later.
In JP-A-2006-140411, an example of the CCD-type solid-state imaging device is described, and an example of a configuration using transfer electrodes of vertical transfer resistors as readout electrodes is described.